The Hydra-Sandhawk program was essentially a systems development program that became operational during development testing. This program was a classic “success” oriented program with an extremely limited budget and no room for errors.
Launch expeditions, flight vehicle components vehicle assembly, ship deployment of a floating launcher/sounding rocket and successful launchings involved many complexities that do not exist with surface launched sounding rockets. While Hydra-Sandhawk was a continuation of the Hydra-Iris program, there was no similarity in rocket motors, flight hardware and the floating launcher was totally new. All the Hydra-Sandhawk systems and components were totally new and untested for underwater sea launches.
- TE-M-473 second stage motor (Thiokol)
- NOTS 401A booster motor (Naval Ordinance Test Station China Lake)
- Payload adapter ring and launch hooks (Naval Missile Center)
- Inter-stage assembly and launch hooks (Naval Missile Center)
- Unique TE-M-473 main flight fins (Naval Missile Center)
- “Marman clamp” stage separation hardware (Naval Missile Center)
- NOTS 401A booster motor fins (Naval Missile Center)
- NOTS 401A booster motor aft ring and launch hook assembly (Naval Missile Center)
- Booster motor release mechanism (Naval Missile Center)
- The vertical sensing, fire control systems (Naval Missile Center)
- TE-M-473 ignition system (Naval Missile Center)
- Modular floating launcher (Naval Missile Center)
- Rocket and launcher assembly dolly (Naval Missile Center)
- Hardware integration testing
- Component fit and function testing.
- Electrical integration testing
- Floatation testing
- A trial run
- Booster only launch
- Launch expeditions
In addition to various systems testing, critical shipboard assembly and operating procedures were also developed during pre-launch testing for launch expeditions using two different ships.
Flight hardware production, development testing and operational launching were all completed without the continuing services of the primary Hydra-Sandhawk designer, Mr. William J. (Billy) Bolster, who had moved on to design new sounding rocket systems for NASA. Component acquisition, production, testing and launch expeditions were managed by Mr. Roger Sanders, an engineer in the Systems Test Division at the Naval Missile Center.
Amazingly, with a couple of minor exceptions, everything that Billy Bolster designed, functioned properly! It’s easy to envision a room full of draftsmen and engineers with slide rules and an unlimited budget to develop and test hardware back then. Billy had none of this. He did it from his one-man office at the Naval Missile Center, well before personal computers, CAD/CAM, spreadsheets and databases. He did not have the luxury of design margin testing to verify that critical structures and components would withstand worst-case conditions. He had no opportunity to verify that various components fit and functioned properly before they were put into production.
He did it with the help of a few dedicated Naval Missile Center technicians and engineers, all having many other responsibilities, in addition to this “no priority” sounding rocket program. The success of the various systems and subsystems designs, the testing and successful launches were a testament to the amazing design skills of Mr. Bolster.
1. Hardware Integration Testing:
Eight sets of flight hardware were procured and were a main focus of integration testing. Two or three sets of flight hardware were used in various testing before the first launch. The flight hardware procurement was of special concern in that none of the many components would go through any kind of pre-production design testing or real design margin testing. Severe budget and time constraints also precluded the flight hardware from being produced by a Mil-Q-9858 compliant manufacturer.
Considerable effort was involved in making sure that all the flight hardware components fit together properly, mechanically functioned properly and electrically functioned properly before any launches. These components required minimum rework in spite of the manufacturer not complying with Mil-Q-9858 quality assurance requirements.
There was concern that the adhesively bonded, plastic honeycomb composite and aluminum base flight fins may not stay together during flight max Q. Basic sine sweep and random vibration testing using Navy missile test levels was done on selected flight fins. No sign of bonding deterioration was found. Underwater testing of the fins was also conducted with fins submerged to 15 feet. X-Rays showed a latent design defect. The fins leaked slightly when submerged! While this was not a problem for any normal, surface launched sounding rocket, it could be fatal to a sounding rocket that has its fins submerged in water, 15 feet below the surface for many hours. Rapidly boiling water inside the fins during max Q could blow the fins apart. Special waterproofing coatings were developed to minimize water absorption.
Also, the marman clamp assembly holding the two stages together had a problem. The stainless cable system holding the marman clamp sections together turned out to be extremely difficult to properly assemble, secure and verify that the stainless cable was sufficiently tight. A loose marman clamp meant that the booster could separate from the big TE-M-473 motor while they were attached to the launch rail and being tossed around by wave action before booster ignition. Or, if the sections separated during boost, the TE-M-473 motor would not ignite and this second stage motor and payload would tumble into the ocean after a very short flight. No design improvements were made.
Various functional tests of the booster ignition, marman clamp seperation and sustainer ignition were performed. Special igniter mounting and water proofing techniques were developed. O-ring seals were the primary waterproofing, but they were backed up with silicone adhesive. If there was one item that made the Hydra-Sandhawk system successful, it was Dow Corning silicone adhesive. If a little red silicone adhesive was required, a lot more was applied.
2. Rocket, assembly dolly and launcher fit and function testing.
The next series of tests at the Naval Missile Center involved structural testing of the launcher to insure that the deployment and retrieval lifting hardware were adequate and functioned properly. This was followed by the assembly of dummy flight vehicle components together with the modular floating launcher, using the specially designed assembly dolly. This was done to insure that all components would assemble properly. Procedures were also developed to properly assemble the rocket and launcher aboard ship using live ordnance and live rocket motors.
Various sub-system and component fit tests were also conducted with live ordnance and live rocket motors to insure that all the real flight components would fit and function properly.
3. Rocket and launcher systems electrical integration and testing
Two of the four launcher floatation cylinders contained the command/control system canisters. The vertical sensing gyros and fire control system, yellow canister was attached to the backbone of the launcher. A quick disconnect umbilical cable was attached to the payload section and held under spring tension by a bracket attached to the launcher. All these subsystems were tested together on the launcher to insure that they would fit and function properly.
4. System floatation testing
The first big test of the launcher and dummy sounding rocket system was to deploy it in the Port Hueneme harbor and see how, or if it floated. This also provided an opportunity to begin to develop launcher deployment and recovery processes. No, it did not sink! The system did float properly. Deployment and recovery processes were developed.
5. Deployment and recovery operations testing, a trial run. See photos in: A Trial Run
A complete trial run, short launch expedition with the launcher, the big assembly dolly and dummy flight vehicle components were required before the first live ordinance, booster only test was attempted. This provided the opportunity to finish development of all the many procedures to properly assemble everything aboard ship, and to deploy and recover the launcher and dummy flight vehicle while at sea. This test was to be a duplicate of the first planned launch, a booster only launch. Unfortunately, the only operational photos to survive are of this trial run.
While there were many logistic, procedural and hardware issues that were identified and resolved, the most difficult problem was the scheduling of an appropriate ship. Two local ships were potentially available for launch expeditions, the USS Norton Sound AVM-1and the USNS Wheeling T-AGM-8. Hydra-Sandhawk had no Navy priority and these ships were involved in high priority Navy missile testing and data acquisition. Problems were compounded by the program having no Navy priority during the Viet Nam war era. Even the classified, dual nature of the payload objectives was insufficient to establish sufficient Navy priority to enable predictable ship scheduling. The problem was never solved. Testing and full launch expeditions were eventually able to be scheduled, seemingly out of sympathy from a couple of Navy Captains.
This trial run was completed using the USS Norton Sound on a one-day trip to the waters near San Nicolas Island. Modifications were required on the fantail to accommodate the Instrumentation and Flight Support trailer which provided communication and launch control. The Norton Sound was originally designed as a WWII, PBY seaplane tender and its crane was perfectly suited for Hydra-Sandhawk deployment and recovery.
The dummy flight vehicle and the launcher were assembled aboard ship using the assembly dolly. All the instrumentation systems were installed. The Hydra-Sandhawk was lowered over the side of the ship. The explosive bolts attaching the launcher were fired and the Hydra-Sandhawk was released in deep water for the first time. Away it floated with the help of a motor whale boat and Seabee divers. After an hour of floating, the launcher and dummy missile were successfully recovered using the launcher’s recovery boom. Hydra-Sandhawk was now all ready for a real launch!
6. Booster only launch and launcher recovery
The Booster only launch was a duplication of the trial run. A live rocket motor with hundreds of pounds of propellant made the one day operation quite different however. The big question was would this thing launch and fly properly? It did! The NOTS booster boiled seawater in a big way and clawed its way up from the ocean. The vehicle flew extremely straight under boost with no measurable roll rate and it simply disappeared into the sky and was never seen again, other than on radar. It no doubt came back down from several miles up, hitting the water at transonic speeds.
A note about the photos and colors: Live NOTS 401-A booster motors can be distinguished from the dummy motor because they were painted DayGlo red. The dummy motor used in all the assembly testing and the trial run was painted white. The dummy payload section was also painted DayGlo red. The dummy payload was well worn after a year of fit testing and floatation testing. It was actually made of 13 inches of laminated plywood and about 5 feet long, turned to a simple cone shape on a large lathe. Real payloads had aluminum skins and were ogive shaped.
There are only two surviving launch photos. One photo shows the Hydra-Sandhawk on boost, about 25’ above the surface and the other shows the rocket about 1,000 feet up. The small size of the booster’s fins and the main flight fins can be clearly seen.
7. Full launch and launcher recovery expeditions.
Hydra-Sandhawk went operational immediately after the successful booster only test. The operational launch expeditions were also final systems tests to verify that the many vibration, structural, thermal and aerodynamic design details were correct.
The first operational launch/first full systems test was conducted in November 1971 using the USS Norton Sound as the support ship. Two trailers, or huts were securely attached to the fantail of the Norton Sound. One was used for the command/control systems and another for final payload assembly. This launch occurred about 800 miles off the coast of Southern California. Its story is on the home page titled “The Long Night”. The Sandhawk, with the Lawrence Radiation Laboratory X-ray payload achieved an apogee of about 165 miles. The floating launcher was successfully recovered the next morning and required little rework to be usable again. The launcher’s paint was becoming quite worn, but no funds were available for cosmetic improvements.
This first flight vehicle can be identified in pictures by the simple DayGlo red paint that Lawrence Radiation laboratory technicians applied to the tip of their payload’s aluminum skin. No photos remain of this evening deployment and morning recovery operations. No photos of the launch are available and would be of little value because the launch took place at midnight, several miles from the ship.
The second launch expedition was conducted in April 1973 using the USNS Wheeling. The Wheeling was a much more difficult support ship. Unlike the Norton Sound and its seaplane tender crane, a large crane had to be welded to the fantail of the Wheeling. Deployment and recovery operations were more difficult because the crane operator had no vision of the actual deployment, or of the difficult process of reattaching the empty launcher to the crane following launch. This launch occurred in about the same location as the first launch. The Sandhawk and payload achieved an apogee of about 160 miles. This time Lawrence Radiation laboratory technicians painted their payload phenolic skin with DayGlo red flames on the front half, which can be seen in some photos.
These two launches were successful, but the quality of X-ray data was degraded by excessive coning angles as both payloads left the atmosphere. The excess coning angles could have been caused by flight fins that had adsorbed water during their being submerged for many hours. It could also have been caused by small deficiencies in aerodynamic design.
The AEC canceled the Hydra-Sandhawk program before the needed design improvements could be identified. It’s likely that the program was canceled because of new international nuclear testing agreements and because X-ray satellites were being developed whose data accumulation time far exceeded the five minutes that Hydra-Sandhawk payloads were out of the atmosphere. X-ray data satellites began with OSO3 in the 1960s. The Vela satellites followed, which were designed to monitor X-rays from high altitude nuclear testing. These were followed by Uhuru, a dedicated X-ray astronomy satellite that provided the first complete X-ray map of the sky. Many other X-ray satellites followed.